The problem for me, as a long time NYC resident, is that there's no other place in America I want to live even with work from home as a possibility. I like mass transit. I like not owning a car. I like that the city is generally safer than the rest of America. I like that it's the center for tech on the east coast, the arts for the entire country, and finance for most of the world. I like that we generally get along…
I see Boston as the tech hub of the East more than NYC. New York obviously has a large number of tech jobs, but Boston and DC both have a higher concentration of tech; in NYC the big fish is obviously finance. I discount DC a little because a lot of that is government and defense related (not a bad thing, just not my cup of tea). Boston has a lot of diversity in tech, lots of health/pharma like Moderna, web companies…
The Boston tech scene and culture (outside of physically being on the MIT campus) is awful. TripAdvisor and Wayfair, your examples, are two companies I would aggressively advise any friends from even talking to. While all the major players are there now it took them a long time to get there. Comp in Boston still lags NY and SF considerably, and in general Boston has always had a resistance to anything "new", it's politically liberal but otherwise a very conservative city. The biotech companies there have always been way more heavy on the bio than the tech. I've worked for Boston area tech companies multiple times , before and after the tech boom, and would never work for a Boston area tech company again.
NYC is on a whole other level. Not only do you have all the major players with much larger campuses there are far more startups and early IPO companies. There is the also entire world of HFT companies (Boston's finance scene is largely very old school investment management companies) which alone would be worthy of making NYC a techhub. I also disagree with your claims about the concentrate of tech companies. Tech related meetups and events in NYC are much larger, more active and have more exciting participants than in the Boston area.